| Movement is one primary way in which vertebrates interact with their environment. One understudied category of movement is the terrestrial locomotion of amphibious fishes, as most descriptions of the mechanics of fish locomotion are largely anecdotal. This dissertation explores the aquatic and terrestrial locomotor modes of three types of amphibious fishes: mudskippers (Gobiidae Periophthalmus argentilineatus), ropefish (Polypteridae Erpetoichthys calabaricus), and walking catfishes (Clariidae Clarias batrachus, Clarias gariepinus). It also examines the transition from aquatic to terrestrial habitats in the ropefish and how terrestrial locomotion varies between two walking catfish species and a non-walking catfish. High-speed videography recorded the locomotion of these fishes. Locomotor trials were digitized and kinematic parameters were calculated from the digitized data. Variables were analyzed using principal components analysis, ANOVA's, and matched pairs t-test. Aquatic and terrestrial locomotor patterns differed for all three categories of amphibious fishes. Mudskippers exhibited an increased pectoral fin stride length in terrestrial locomotion, and the timing of pectoral fin depression varied between habitats. However, I found no difference in fin orientation between habitats. Ropefish exhibited long, slow, high-amplitude undulations along the length of the body during terrestrial locomotion. In contrast, aquatic locomotion was characterized by undulations that gradually increase in an anterior-to-posterior direction and have shorter wavelengths, smaller amplitudes, and higher frequencies compared to terrestrial locomotion. In addition, there was no clear transition between locomotor modes in treatments with intermediate water levels. Instead, locomotion in these treatments shared characteristics with both aquatic and terrestrial locomotion. Aquatic locomotion of walking catfishes was similar to that of the ropefish. However, terrestrial locomotion was characterized by contact between a pectoral fin spine and the ground, while the axial musculature and tail push against the ground to elevate the catfish over the spine. Terrestrial locomotion was broadly similar between the walking catfishes, although differences existed between them in minimum fin angle and the amount of fin angle off-set. Additionally, terrestrial locomotion in the non-walking catfish differed from the walking catfishes in variables indicating effectiveness of movement (e.g speed, tail and pectoral fin stride lengths), but was surprisingly not very different in the actual movement patterns produced. |
